January Jones didn't mince her words when speaking out about Las Vegas shooter Stephen Paddock, who killed at least 50 people and injured more than 400 others on Sunday, October 1, in the deadliest mass shooting in U.S. history.

January Jones attends the Hammer Museum's 14th Annual Gala in the Garden at Hammer Museum in Westwood, California, on October 8, 2016.Tibrina Hobson/WireImage

"Stephen Paddock is a white US citizen and he is a terrorist," the Mad Men alum, 39, wrote on Instagram on Monday, October 2. "Also if you're going to #prayforvegas you must also #voteforguncontrol #protestforguncontrol."

Jones captioned her post with an emoji of a broken heart. Additionally, she disabled the ability to comment on the post, likely in anticipation of criticism for calling Paddock a "terrorist."

Police said Paddock had no known connection to terrorism. "We have to establish what his motivation was first," Las Vegas Metropolitan Police Department Sheriff Joseph Lombardo said during a news conference on Monday. However, many social media users have labeled the shooting as an act of terrorism.

Paddock, a 64-year-old resident of Mesquite, Nevada, died of what law enforcement believe was a self-inflicted gunshot wound shortly after he opened fire on a crowd of 30,000 country music festivalgoers from the 32nd floor of the nearby Mandalay Bay Resort and Casino. Police discovered at least 10 rifles inside Paddock's hotel room.

The gunman's brother Eric Hudson Paddock told NBC News on Monday morning that he had "no idea" why Stephen committed the shooting. "Mars just fell into the earth. We're completely dumbfounded," Eric said of his family's response. "We are completely at a loss."

President Donald Trump announced during a press conference that he will visit Las Vegas on Wednesday, October 4, to meet with first responders, victims and their families.

People trying to locate missing loved ones are being asked to call 1-866-535-5654.